The present invention relates to in-vehicle audio/video systems.
In an existing in-vehicle audio/video system, a display device is mounted within the vehicle and signals are either received over-the-air or from a direct connection such as a video tape player or digital video disk (DVD) player. The video programming is sent to the display device, while the corresponding audio programming is sent to the vehicle radio over a coaxial cable. To listen to the audio programming, the vehicle occupant tunes the built-in vehicle radio to a predetermined station according to settings on the attached video player.
One problem with these existing systems is that the coaxial cable connecting the video player and display device to the built-in vehicle radio makes after market installation rather difficult. As such, with existing in-vehicle systems, it is preferred that the system is set up while the interior vehicle is being put together. Another existing system attempts to address this problem by eliminating the coaxial cable. This type of system broadcasts the audio signal at low power within the vehicle so that the built-in radio may be tuned to a predetermined channel and receive the system audio channel. However, because the radio spectrum is rather crowded, it is sometimes difficult to lock onto the system audio channel due to noise from other channels, particularly in the frequency modulation (FM) radio spectrum.
For the foregoing reasons, there is a need for in-vehicle audio/video system that facilitates after market installation.
It is, therefore, an object of the present invention to provide an in-vehicle audio/video system wherein audio programming is broadcast within the vehicle at low power over a system audio channel, in which a tuner and range adjuster are operable in first and second modes having a full bandwidth and a restricted bandwidth, respectively, to allow fine tuning by the tuner of the system audio channel.
In carrying out the above object, a wireless radio frequency receiver for an in-vehicle audio/video system is provided. Video programming is sent to a display device and corresponding audio programming is broadcast within the vehicle at low power over a system audio channel. The receiver comprises an antenna, a tuner, and a frequency range adjuster. The tuner is coupled to the antenna and has an output at a received channel. The tuner has an adjustable component that is adjusted to select the received channel from a selectable frequency range. The frequency range adjuster is coupled to the tuner, and is operable in first and second modes. The range adjuster is configured such that the first mode selects the frequency range for the tuner as a full range including local broadcast channels, with the full range having a first bandwidth. Further, the range adjuster is configured such that the second mode selects the frequency range as a restricted range including the system audio channel, with the restricted range having a second bandwidth that is significantly less than the first bandwidth to allow fine tuning by the tuner of the system audio channel.
Preferably, the audio programming is broadcast as a frequency modulated signal and the receiver further comprises a frequency demodulator coupled to the tuner output. Additionally, in a preferred construction, a down converter is located between the tuner output and the frequency demodulator.
Further, in a preferred embodiment, the tuner includes a voltage controlled capacitance. The frequency range adjuster is operative to select the frequency range by supplying a first voltage to the tuner when operating in the first mode, and by supplying a second voltage to the tuner when operating in the second mode. The voltage controlled capacitance may be, for example, a tuning diode with the adjustable component of the tuner selecting the received channel by applying a portion of the supplied voltage to the tuning diode. An audio amplifier is coupled to the demodulator, and speakers are coupled to the audio amplifier.
Further, in carrying out the present invention, a headset for an in-vehicle audio/video system is provided. Video programming is sent to a display device and corresponding audio programming is broadcast within the vehicle at low power over a system audio channel. The headset comprises a main body and a wireless radio frequency receiver attached to the main body. The receiver includes a tuner coupled to an antenna, and a frequency range adjuster coupled to the tuner. The range adjuster is operable in first and second modes. The range adjuster is configured such that the first mode selects the frequency range as a fall range with a first bandwidth, and such that the second mode selects the frequency range as a restricted range including the system audio channel and having a second bandwidth. The second bandwidth is significantly less than the first bandwidth to allow fine tuning of by the tuner of the system audio channel.
Still further, in carrying out the present invention, an in-vehicle audio/video system wherein audio programming is broadcast within the vehicle at low power over a system audio channel is provided. The system comprises a display device for receiving video programming, and a wireless radio frequency receiver. The receiver includes a tuner coupled to an antenna and having an output at a received channel. The tuner has an adjustable component that is adjusted to select the received channel from a selectable frequency range. The receiver further includes a frequency range adjuster coupled to the tuner, and the range adjuster is operable in first and second modes. Operating the range adjuster in the first mode selects the frequency range as a full range including local broadcast channels and having a first bandwidth. Operating the range adjuster in the second mode selects the frequency range as a restricted range including the system audio channel and having a second bandwidth. The second bandwidth is significantly less than the first bandwidth to allow fine tuning by the tuner of the system audio channel.
In one embodiment, the system further comprises an audio/video source operative to provide the video programming to the display device and to broadcast the audio programming within the vehicle at low power over the system audio channel. The audio/video source may be in a variety of different forms such as, for example, a video player or a video game system. Further, the audio/video source may be a main antenna coupled to the display device and operative to receive over-the-air audio and video programming, and a converter coupled to the main antenna. The converter converts the audio programming to allow broadcasting of the audio programming within the vehicle at low power over the system audio channel.
Even further, in carrying out the present invention, an in-vehicle audio/video system wherein audio programming is broadcast within the vehicle at low power over a system audio channel is provided. The system comprises a display device, and a wireless radio frequency receiver. The receiver includes a frequency range adjuster coupled to the tuner and operable in first and second modes. In the first mode, the range adjuster selects the frequency range as about 88 megahertz to about 108 megahertz. In the second mode, the range adjuster selects the frequency range as a restricted range that preferably is about 88 megahertz to about 92 megahertz to allow fine tuning by the tuner of the system audio channel, with the system audio channel being within the restricted bandwidth of the second operating mode.
In one embodiment, the range adjuster includes a switch having a first position that causes the range adjuster to operate in the first mode, and a second position that causes the range adjuster to operate in the second mode,
The advantages associated with embodiments of the present invention are numerous. For example, embodiments of the present invention facilitate after market installation of an in-vehicle audio/video system. Still further, embodiments of the present invention allow a headset to be switched between a normal full range mode, and a special restricted range mode for receiving the system audio channel. By restricting the overall bandwidth, while using the same physical or mechanical range for the tuner, the restricted bandwidth allows finer tuning. As such, in preferred embodiments, the audio/video source is configured to allow a user to select the system audio channel from a plurality of channels between about 88 megahertz and about 92 megahertz. In turn, a switch on a user headset allows the user to switch between the normal frequency modulation (FM) bandwidth, and a restricted bandwidth, preferably a subset of the full bandwidth, to allow fine tuning of the system audio channel.
In some embodiments of the present invention, it may be desirable to use the built-in vehicle receiver to receive the system audio channel, in addition to using any wireless receivers. If it is expected that the built-in receiver will be used in such a way, some embodiments of the present invention optionally provide a transmission line having a first end connected to built-in receiver. The second end of the transmission line should be located within the vehicle, and defines an antenna for receiving the low power broadcast. Effectively, this gives the built-in receiver two antennas. The first antenna is the traditional, outside of the vehicle, antenna, while the second antenna is defined at the end of the transmission line. This is advantageous in that because the system audio channel is broadcast at low power, it may (in some instances) be easier to receive with an antenna that is within the vehicle. In one suitable implementation, a Y connection in a wiring box at the back of the built-in receiver allows one branch to go to the outdoor antenna, and allows the other branch to end at an antenna near the low power audio signal source within the vehicle. Of course, it is appreciated that appropriate steps may need to be taken to reduce impedance problems on the transmission line. For example, a 4.7 pF capacitor may be placed along the inside antenna drop.
The above object and other objects, features, and advantages of the present invention are readily apparent from the following detailed description of the best mode for carrying out the invention when taken in connection with the accompanying drawings.